Green synthesis and characterisation of L-Serine capped magnetite nanoparticles for removal of Rhodamine B from contaminated water

Figures & data

Figure 1. UV-Visible spectra of (a) uncapped and (b) L-Ser capped Fe₃O₄ NPs.

Figure 2. The powder XRD patterns of (a) uncapped Fe₃O₄ NPs and (b) L-Ser capped Fe₃O₄ NPs.

Figure 3. FTIR spectra of (a) uncapped and (b) L-Ser capped Fe₃O₄ NPs.

Figure 4. Representative SEM images (a–c) of L-Ser capped Fe₃O₄ and (d) EDS spectrum and the relative percent weight analysis (inset) of L-Ser capped Fe₃O₄ NPs.

Figure 5. (a,b) Representative TEM images of L-Ser capped Fe₃O₄ NPs, (c) selected area electron diffraction patterns and (d) size distribution histogram.

Figure 6. Vibrating sample magnetometer (VSM) curve of L-Ser capped Fe₃O₄ NPs at room temperature.

Scheme 1. Effect pH on charge of L-Serine.

Figure 7. Plausible interaction mechanisms of L-Ser to Fe₃O₄ NPs through (a) carboxyl bi-dentate, (b) carboxyl mono-dentate and (c) amino groups.

Figure 8. (a) Effect of adsorbent type for adsorption of RhB (5 mg⋅L⁻¹) and (b) effect of RhB concentration on percent removal (%) onto L-Ser capped Fe₃O₄ NPs.

Figure 9. (a) Pseudo-first-order and (b) pseudo-second-order plots for adsorption of RhB on L-Ser capped Fe₃O₄ NPs at varying initial concentration of RhB (error bar represents 5% error).

Table 1. The pseudo-first-order and pseudo-second-order kinetics parameters of RhB adsorption on L-Ser capped Fe₃O₄ NPs.

	Initial concentration of dye
Parameters	5 ppm	10 ppm	15 ppm
qe,exp. (mg⋅g)	4.276	6.561	6.82
Pseudo-first-order kinetics
k1 (min^−1)	0.01492	0.01812	0.02222
qecal (mg/g)	2.723	6.11	4.739
R^2	0.8489	0.9756	0.9605
Pseudo-second-order kinetics
k2 (g/mg/min)	0.048	0.0185	0.0296
qecal (mg/g)	4.535	7.940	7.270
R^2	0.991	0.99	0.997

Figure 10. (a) Effect of RhB concentration on amount of dye adsorbed on L-Ser capped Fe₃O₄ NPs (q_t), (b) Langmuir isotherm, (c) Freundlich isotherm (d) Tempkin isotherm models.

Table 2. Langmuir, Freundlich and Tempkin adsorption isotherms’ parameters for the adsorption of RhB onto L-Ser capped Fe₃O₄ NPs.

Isotherm models	Parameters
Langmuir	Qo (mg/g)	bL(L/mg)	RL	R^2
	7.19	2.31	0.03–0.08	0.99
Freundulich	1/n	kf (mg^1−1/^n⋅L^1/^n⋅g^−1)		R^2
	0.2	4.7		0.85
Tempkin	bT/RT (J/mol)	aT (L/mg)		R^2
	0.914	79.12		0.87

Figure 11. Effect of temperature on (a) adsorption efficiency and (b) van't Hoff plot (5% error bar) for adsorption of RhB (10 ppm) onto of L-Ser capped Fe₃O₄ NPs.

Table 3. Thermodynamic parameters for the adsorption of RhB onto L-Ser capped Fe₃O₄ NPs.

Temperature	∆G^ο	∆H^ο	∆S^ο
K	kJ⋅mol^−1	kJ⋅mol^−1	kJ⋅mol^−1⋅K^−1
290	−0.458
300	−1.165	41.75	0.145
310	−2.595
320	−4.025